Left ventricular contractility normally accelerates blood within the left ventricle and ejects as an average 70% of the blood volume contained in the left ventricle into the circulatory system. In case of severe heart failure this mechanism is insufficient and the majority of the blood volume remains within the ventricle, thus producing inadequate cardiac output.
Several systems are known to correct cardiac failure bypassing the left ventricle and continuously ejecting the blood from the left ventricle via an artificial conduit directly into the great thoracic arteries. Such systems operate as left ventricular assist devices (LVAD) in order to help the heart's weakened left ventricle pump blood throughout the body.
The LVAD can be used as a bridge-to-transplant, which means it can help a patient survive until a donor heart becomes available for transplant. This option may be appropriate for people whose medical therapy has failed acutely and/or who are hospitalized with end-stage systolic heart failure. The LVAD also can be used as destination therapy, which is an alternative to heart transplantation. Destination therapy provides long-term support in patients who are not candidates for transplant, because of severe comorbidities and especially of older age. When used as a bridge-to-transplant or as destination therapy, the LVAD provides effective chronic hemodynamic support, maintains or improves other organ function, improves exercise performance and enables participation in cardiac rehabilitation.
These assist devices comprise a continuous flow pump, which produces a continuous, non-pulsatile flow of blood through the circulatory system using a rotary pumping mechanism. There is, however, a multitude of side effects on end organs as well as major cardiac surgery for implantation. Recently several minimal invasive forms of cardiac assist devices have been developed. WO 2009/099644 A1 discloses a ventricular assist device for intraventricular placement inside a human heart. It comprises a pump that is implanted within the left ventricle with the outflow cannula projecting through the aortic valve and terminating short of the aortic arch. The pump is fixed to the wall of the heart near the apex by means of an anchor element in order to hold the pump and the outflow cannula in position. The device disclosed in WO 2009/099644 A1 produces a continuous flow of blood, wherein the aortic valve is penetrated by the outflow cannula and is therefore unable to close effectively, but cooperates with the pump traversing it in order to prevent retrograde flow of blood into the left ventricle during diastole. Because of the continuous character of the flow the valve is held in only one position, which increases the risk of valve thrombosis and/or significant retrograde leakage into the failing and assisted ventricle.
The drawback of the device disclosed in WO 2009/099644 A1 and of other continuous flow ventricular assist devices is that—since they have to maintain up to 100% of cardiac output—they are disturbing normal end organ function and contractile pattern of the diseased heart, leaving nutritive coronary blood flow unchanged and therefore limit structural recovery.